In the coming year we will continue studying the hemodynamic, metabolic, and bacteriologic response of the newborn and maturing organism to aerobic, anaerobic, and combined anaerobic and aerobic peritonitis. Completed investigations with the aerobic organism, E. coli., suggest that there is little age-related difference in these physiologic responses. Profound hypolycemia develops as insulin levels rise and cardiac index falls. Bacteria proliferate in the peritoneal cavity, particularly in the newborn animal, and persistent bacteremia develops. At the present time the effects of experimental peritonitis using the anaerobic organism, Bacteroides fragilis, on animals of different age groups is being studied. Ultimately our model will be used to investigate the responses to peritonitis resulting from a mixture of these two organisms.